Self-rectifying fluid pump



Dec. 29, 1959 L C, F|SHER 2,918,875

SELF-RECTIFYING FLUID PUMP INVENTOR. JOHN C. FISHER ATTORN EYS Dec. 29, 1959 J. c. FISHER 2,918,875

SELF-RECTIFYING FLUID PUMP Filed April 25, 1957 s sheets-sheer 2 Fg.2 46 l 1 INVENTOR. JoHNc. FISHER KENWAY, JENNEY, WITTER a HILDREM ATTORNEYS Dec. 29, 1959 c. FISHER 2,918,875

SELF-RECTIFYING FLUID PUMP Filed April 25, 1957 s sheets-sheet s INVENTOR. JOHN C. FISHER BY KENWAY. JENNEY, wmsn a HILDREIH ATTORNEYS United States Patent O z,91s,s7s

SELF-RECTIFYING FLUID PUMP John C. Fisher, Cambridge, Mass.

Application April 23, 1957, Serial No. 654,597 E6 claims. (ci. 10s-16) This invention relates to a self-rectifying iluid pump of the accelerator-tube type which is particularly suitable for biological and laboratory uses, such as pumping blood, blood plasma, bacterial solutions, etc.

Displacement, rotary and centrifugal type pumps not only embody one or more impellers and other moving parts with which the liquid being pumped comes in contact, but also a power-transmitting element driven from an external source which requires packing glands and the like seals to prevent leakage. When such pumps are used to transmit liquids of the aforementioned type, they are not only apt to introduce contamination into the liquid, but they are apt to destroy or injure living cells or organisms contained in such liquids.

The principal objects of the invention are to overcome the aforementioned diliiculties and provide a self-rectifying pump having the inherent advantages of the accelerator-tube type, but which does not require the use of valves, packing glands, a fluid impeller and the like parts which come in contact with the liquid being pumped and which might cause damage to blood cells, bacteria or other solids or semi-solids carried in liquid suspension.

Another object is to provide a pump having a nonpulsating discharge and free from parts that might produce a shearing or crushing action on the liquid being pumped, such as occurs in peristaltic pumps.

These and other objects, aspects and features of the invention Will be apparent from a consideration of the following disclosure and the accompanying drawings, wherein:

Fig. l is a view, with parts shown in section, illustrating the principle underlying the invention;

Fig. 2 is a front elevation of a pump constructed in accordance with the present invention;

Fig. 3 is a side elevation of the pump shown in Fig. 2; and

Fig. 4 is a schematic View illustrating the mode of operation of the pump shown in Figs. 2 and 3.

In accordance with the present invention my improved pump comprises a length of tubing having opposed sections mounted on angularly oscillating arms, plates or the like supports, the opposed sections being interconnected with an intake and a discharge by ilexible sections in such a manner as to create additive pressure gradients along the length of the tubing when the supports are simultaneously oscillated in opposite directions thereby to produce a uniform, non-pulsating discharge. In order to appreciate the principle involved, reference may be had to Fig. 1 wherein an elongated hollow member, which in the specitic embodiment shown is a rigid, closed tube 1, is completely iilled with a liquid mass of density m, and is secured to an angularly oscillating arm 2 by means of clamps 3, both the arm and the tube being subjected to a simple harmonic angular oscillation of velocity S2 about a x'ed axis of rotation 4 by any suitable prime mover capable of producing such motion.

At any point within the liquid, such as P, at a distance sol ICC

r from the axis of rotation, there will be two components of acceleration due to the angular oscillation. One component of acceleration is tangential, i.e. at 90 to the long axis of the tube, and of magnitude:

i dsl ag-TE l l where at is the tangential component of acceleration; r is the distance of thepoint P from the axis of rotation;

is the angular acceleration of the tube and arm; t is time, measured from any convenient instant.

The second component of acceleration at point P is centripetal, i.e. parallel to the radius from the center of rotation to P and directed toward the axis 4, and of magnitude:

M m2 v (2) where am, is the centripetal component of acceleration;` r is the distance of P from the axis of rotation; Q is the angular velocity of the tube.

Substitution of (3) into (2) yields an' expression for the magnitude of the centripetal acceleration at any instant in time:

ap=r22=r2 sin wt Y (4) Now substitution into (4) of the identity sin @En-cos zat) (5) gives us the expression I Equation 6 showsthat the centripetal acceleration consists of two parts:

an average or constant value of magnitude and a double-frequency alternating acceleration -of amplitude Note that in yquations 3, 4, 5, and 6, w denotes the frequency (in radian measure) of the angular oscillation.

By applying the fundamental dilerentialf equation for an incompressible liquid, where frictional forces and changes of elevation may be neglected if their effects are small by comparison with the effects of the inertial forces,

the radial acceleration within the liquid at any point P may be related to the pressure gradient at this point:

where Apio: `[munir where Apio is the rise in pressure from the inner end of the liquid column to the outer end;

m is the mass density of the liquid, m=w/g;

ar is the radial acceleration, and is equal to am as dened by Equation 6;

dr is the differential change in radius r.

Substitution of Equation 6 into Equation l() yields ma Ap.,=t22(lcos Qwfrdr Then, performing the indicated integration, we obtain ma T2 Ra A t0= 2 p 2&2 (l eos 2wt)2]Ri (l2) and evaluating the integrated result at the limits Ro and R, gives us the expression for the pressure difference between the ends of the enclosed liquid column of Figure l as mx Ap-=EQ2(l-cos 2wt)(R2-R,2) (13) The arithmetical average radius of the column may be expressed as R.=R,VR" 14) and the radial length of the column as S=R0-R, (15) Substitution of (14) and (15 into (13) reduces the expression for the pressure difference to Equation 16 shows that the total pressure difference across the ends of the liquid column in Figure l is made up of two parts: a steady pressure difference, and a pressure difference which alternates at twice the frequency of the angular oscillation of the arm and tube. Hence, if the inner and outer ends of tube l are suitably connected via flexible sections, such as helices, to some external apparatus, the steady pressure difference of Equation l6 can be used to produce a unidirectional liquid flow in this apparatus, without the need for rectifying valves. By means hereinafter explained, it is possible to eliminate the alternating part of the total pres- Ap cos 2wt (16) sure difference in Equation 16, so that the liquid flow is perfectly smooth (free of pulsations).

lt is obvious from the foregoing that the number of radial, oscillating tube sections l may be increased, provided that the number of radial tube sections and the number of flexible sections be equal and be an integermultiple of 4, with half these tube sections driven in angular simple harmonicmotion which is out of time-phase with that of the remaining tube sections Referring to Figs. 2 to 4 which show what is now considcred a preferred embodiment of the invention, the numeral 10 designates a base which may be rigidly secured to a suitable support and projecting upwardly from the base is a central column 12 having two laterally extending bearing-support brackets 14 and i5 and forwardly projecting, horizontally extending shelves 24a and 15a. Shafts lo and 18 are rotatably mounted in the bearings carried by the outer ends of the brackets and the centers of arms 2t) and 22 are secured to these shafts so as to undergo angular oscillations about the axes of their respective shafts. An angular oscillation of sinusoidal time-variation is applied to shaft llo and a cosinusoidal time-variation is applied to shaft 1S by means of connecting links or cranks 24 and 26, respectively, pivotally connected with the upper ends of connecting rods 2S and 31').

The lower ends of the connecting rods are formed with bearing heads connected with eccentric cam 32 fastened to a continuously rotating shaft 35 which is supported by a bearing 36 mounted in the column l2 and two pillow blocks 38 mounted on the base lil. The construction and arrangement of parts is such that the average directions of the connecting rods diverge from each other at an angle of 90. Mounted on the outer end of the shaft 3S is a pulley or sheave 4t) driven by a V-belt and motor (not shown). A flywheel 44 is secured to the shaft 35 to absorb torque pulsations caused by the reciprocating motion of the driven mechanism, the construction and arrangement of parts being such that rotation of the shaft 35 oscillates the connecting rods 28 and 30 which in turn oscillate the cranks 24 and 26 through an angle of suitable magnitude.

A continuous length of plastic or metal tubing 46 extends along the column 12, bracket shelves 14a, 15a, and arms 26, 22 so that the pressure differences produced across the radial tube sections on the oscillating arms are additive around this circuit, it being understood that these parts carry spaced clips 47 and clamps `48 for holding the tubing in place. The intake end 50 of the tubing 46 extends downwardly along the column l2 (indicated by 5l in Figs. 2 and 4), then horizontally forwardly to the bracket shelf 14a (indicated by 52 in Fig. 4), then outwardly along the shelf 14a (indicated by 53 in Figs. 2 and 4), then horizontally rearwardly (indicated by 54, Fig. 4) to the hub of the oscillating arm 20, then upwardly along the arm 2t) (indicated by 55 in Figs. 2 and 4) to the flexible section of helical coil 5a. The tube then proceeds vertically downwardly on column l2 (indi,- cated by 57 in Figs. 2 and 4), then horizontally forwardly (indicated by 58 in Fig. 4), then horizontally along the bracket shelf 14a beneath the run 53 (indicated by 59 in Figs. 2 and 4), then rearwardly to the hub of the arm 20 (indicated by 60 in Fig. 4), then downwardly along the lower end of arm 2t) (indicated by 6l in Figs. 2 and 4) to the coil 62. The tube then proceeds upwardly along the column l2 (indicated by 63 in Figs. 2 and 4), then forwardly to the bracket shelf 15a (indicated by 64 in Fig. 4), then outwardly along bracket shelf 15a (indicated by 65 in Figs. 2 and 4), then rearwardly to the hub of the arm 22 (indicated by 66 in Figs. 3 and 4), then downwardly along the lower end of arm 22 (indicated by 67 in Figs, 2, 3 and 4) to the coil 68. The tube then proceeds upwardly along column 12 (indicated by 69 in Figs. 2 and 4), then forwardly to bracket shelf 15a (indicated by 70 in Fig. 4), then outwardly along bracket shelf a above the tun 65 (indicated by 71 in Figs. 2 and 4), then rearwardly to the hub of the arm 22 (indicated by 72 in Figs. 3 and 4), then upwardly along the arm 22 (indicated by 73' in Figs. ,2r-4), to coil 74, and then to the top ofthe column 12 where it provides the discharge 75.

The coils 56, 62, 68 and 74 are preferably formed of separate pieces of tubing which are suiciently rigid to retain their helical shape, but sufficiently elastic to permit the necessary extension and shortening during the oscillations of the arms and 22 and hence any suitable type of leakproof connections between the coils and the` rest of the tubing may be provided so that it is comparatively easy to insert and remove the tubing and coils.

When the shaft 35 is rotated at constant angular speed, the eccentric cam 32 causes the connecting rods 28 and 30 to impart simple harmonic angular oscillations to the arms 20 and 22. This angular oscillation of each arm has a frequency w, where w is 21r times the number of revolutions per unit time of shaft 35. Because the average directions of the long axes of connecting rods 28 and 30 are 90 apart, while both rods are driven by a single eccentric cam 32, the angular oscillations of arms 20 and 22 are 90 apart in their time phases.

Since the tubing circuit is wound in such a way that the pressure differences across the radial portions of the tubing on arms 20 and 22 are additive, the net pressure difference between the inlet and outlet ends of the complete interior circuit will be the sum of the radially-outward pressure rises in the radial tube sections, of which there are four. If the external flow is completely blocked off, then the total pressure rise contributed by the tubes on arm 20 is given by an expression of the form of Equation 16:

A1020: mSPRamS? mZRam/S cos Zot (17) The angular velocity of arm 20 may be described by Equation 3. arm 22 is 90 out of time-phase with that of arm 20, we may express the velocity of arm 22 as 922:() COS wt Because the centripetal acceleration at each point in the tubes on arm 22 depends upon the square of this angular velocity, and because of the identity cos2 wtEG-l-cos Zwt) (19) it follows that the net pressure rise contributed by the two tube sections carried on arm 22, when the external ow is blocked olf, is given by the vexpression A7022 mSAPRamS-lmZRamS cos 2m (20) When Equation 17 is added to Equation 20, We obtain an expression for the total pressure rise across the entire interior tubing circuit in the blocked-off condition:

Because the alternating components of pressure diierence in (17) and (20) are of opposite sign, they disappear from (2l), and the net pressure difference is simply a constant, unidirectional quantity. This result necessarily follows in view of the fact that sin2 tut-icos2 e151 However, because the angular velocity of to the internal circuit which can sustain an unsteady ow,

even if such unsteady flow should momentarily arise.

While I have shown and described one desirable embodiment of the invention it is to be understood that this disclosure is for the purpose of illustration and that various modifications may be made without departing from the spirit and scope of the invention as set forth in the appended claims.

I claim:

l. A pump comprising a supporting structure, a rocker arm pivotally mounted at its center to said structure to oscillate about a iixed axis, means mounted on said structure for oscillating said arm, an intake and a discharge secured to said structure, a first accelerator tube secured to and extending in one direction along said arm from its pivotal axis outwardly to the end portion of said arm, a second accelerator tube secured to and extending in the opposite direction along said arm from its pivotal axis outwardly to its opposite end portion, inlet ducts carried by said structure interconnecting the inner ends of the irst and second accelerator tubes with said intake and outlet ducts including flexible sections interconnecting the outer ends of said tubes with said discharge.

2. A pump comprising a supporting structure, a rocker arm pivotally mounted at its center to said structure to oscillate about a fixed axis, means mounted on said structure for oscillating said arm, an intake and a discharge secured to said structure, a first accelerator tube secured to and extending in one direction along said arm from its pivotal axis outwardly to the end portion of said arm, a second accelerator tube secured to and extending in the opposite direction along said arm from its pivotal axis outwardly to its opposite end portion, an inlet duct connecting said intake and the inner end of the lirst accelerator tube, a duct having a helical resilient coil connecting the outer end of the first accelerator tube with the inner end of the second accelerator tube, and an outlet duct including a ilexible coil connecting the outer end of the second accelerator tube with said discharge.

3. A pump comprising a supporting structure, a pair of arms pivotally mounted on said structure to oscillate about fixed axes, means mounted on said structure for oscillating said arms simultaneously in opposite directions, .an intake and a discharge secured to said structure, a iirst accelerator tube secured to one of said arms and extending outwardly from its pivotal axis, an inlet duct connecting said intake with the inner end of said lirst accelerator tube, a second accelerator tube secured to and extending along the other arm from its pivotal axis outwardly, a duct having a flexible section connecting the outer end of the first accelerator tube with the inner end of the second accelerator tube, and an outlet duct having a iiexible section connecting the outer end of said second accelerator tube with said discharge.

4. A pump comprising a supporting structure, a pair of rocker arms each pivotally mounted at its center on said structure so as to oscillate about a xed axis, means mounted in said structure for oscillating said arms simultaneously in opposite directions, an intake and a discharge secured to said structure, a first accelerator tube secured to and extending from its pivotal axis outwardly along one arm in one direction, the inner end of said first accelerator tube having a connection with said intake, a first resilient coil connected at one end with the outer end of said irst accelerator tube, a second accelerator tube secured to and extending from its pivotal axis outwardly along said one arm in the opposite direction, the inner end of said second accelerator tube having a connection with the other end of said first coil, a second resilient coil connected at one end with the outer end of said second accelerator tube, a third accelerator tube secured to and extending in one direction from its pivotal axis outwardly along the other of said arms, the inner end of said third accelerator tube having la connection with the other end of said second coil, a third resilient coil connected at one end with the outer end of said third accelerator tube, a fourth accelerator tube secured to `and extending in the opposite direction from its pivotal axis outwardly along said other arm, the inner end of said fourth accelerator tube having a connection with the other end of said third coil, a fourth resilient coil connected at one end to the outer end of said fourth accelerator tube, and an outlet duct connecting the opposite end of said fourth coil with said discharge.

5. A pump comprising a base, an upstanding post mounted on said base, a horizontal shelf secured to said post above said base and extending laterally from each side of said post, two rocker arms each pivotally supported at its center on the opposite end portions of said shelf, means mounted on said base for oscillating the rocker arms simultaneously in opposite directions about fixed axes, an intake mounted on the upper part of said post, a discharge mounted on the upper part of said post, a first accelerator tube having a connection with said intake and extending downwardly along said post to said shelf, then along said shelf to the first arm and along the first arm from its pivotal axis to its upper end, a rst resilient coil disposed above said shelf approximately the level of the upper end of said first arm and connected at one end with the outer end of said rst accelerator tube, a second accelerator tube having a connection with the other end of said rst coil and extending downwardly along said post to said shelf, then along said shelf to said first `arm and along the first arm from its pivotal axis to its lower end, a second resilient coil disposed below said shelf at approximately the level of the lower end of said first arm and connected at one end with the lower end of said second accelerator tube, a third accelerator tube having a connection with the other end of said second coil and extending upwardly along said post to said shelf, then along said shelf to the second arm and along the second arm from its pivotal mounting to its lower end, a third resilient coil disposed below said shelf at approximately the level of the lower end of said second arm and connected at one end with the lower end of said third `accelerator tube, a fourth accelerator tube having a connection with the other end of said third coil and extending upwardly along said post to said shelf, then along said shelf to said second arm and along said second arm from its pivotal mounting to its upper end, a fourth resilient coil disposed yabove said shelf at approximately the level of the upper end of said second arm and connected at one end to the upper end of said fourth accelerator tube, and an outlet duct connecting the opposite end of said fourth coil with said discharge.

6. In a fluid pump, an elongated hollow member in which fluid flow may be induced from one end thereof to the other end thereof, means mounting said member for limited angular oscillation about a fixed axis extending at right angles to said member with both ends of said member being disposed on the same side of said axis and with said one end being disposed closer to said axis than said other end, a second elongated hollow member in which fluid flow may be induced from one end thereof to the other end thereof, means mounting said second member for limited angular oscillation about a xed axis extending at right angles to said second member with both ends of said second member being disposed on the same side of the fixed axis associated therewith and with said one end of said second member being disposed closer to the fixed axis associated therewith than said other end of said second member, means providing a fluid flow connection between said other end `of one of said members and said one end of the other of said members, and means for simultaneously oscillating said members in simple harmonic motion with one of said members being degrees out of time phase with the other of said members.

Alpuohe July 11, 1882 Bodine May 22, 1951 

